Laminated electrode



United States Patent ()fiice A 2,826,623 Patented Mar. 11, 1958 LAMINATED ELECTRODE Leon B. Rosseau, Narberth, Pa., assignor to Aiax Electric Company, Philadelphia, Pa., a corporation of Pennsyh vania Application April 13, 1956, Serial No. 573,068

6 Claims. (Cl. 13--23) This invention relates to electrodes for use with an electric salt bath furnace and, more particularly, to an electrode construction facilitating the cooling thereof and the connection thereof to a bus bar carrying electric current.

The invention is concerned in general with the type of equipment which includes a furnace pot adapted to hold a bath of molten salt maintained at a desired temperature by passing an electric current through the salt between spaced parallel electrode hot legs each of which is interconnected with an electrode cold leg extending out of the furnace to a source of electric current.

Various types of electrodes may be used in a furnace of the kind here involved. For example, electrodes which extend generally vertically upwardly out of the bath and over the top of the pot wall, electrodes which include generally horizontal portions extending through the furnace wall, and electrodes which include a slanting portion extending from a point below the surface of the bath diagonally upwardly to a point above the level of the bath where it is connected to an electrode cold leg. Electrodes of the third mentioned type are fully disclosed and claimed in my copending application Serial No. 577,980, filed April 13, 1956, and assigned to the assignee of the present application.

Customarily electrodes are formed of metal bar stock (usually of rectangular cross section), the metal selected most commonly being a steel capable of withstanding the relatively high temperatures normally encountered during operation of the furnace. Although, as more fully discussed in my copending application above identified, various means may be employed to reduce corrosion of the electrodes, nevertheless it is necessary from time to time to remove the electrodes from the furnace for inspection, maintenance, etc., and it is, therefore, desirable to provide electrodes which can be readily disengaged from the bus bars of the power source.

At the same time, it is important to effect tight interconnection of the electrodes and bus bars during operation in such a manner as to provide suitable paths for the flow of current between the power source and electrodes, such paths preferably including substantial surface contact (rather than merely point or line contact) between the bus bars and electrodes.

It is here noted that, because of its advantageous properties as a conductor, copper is ordinarily a desirable metal from which to construct the power source bus bars and miscellaneous other power source components. It is also desirable, in connection with the hook up and arrangement of the power source, to effect the interconnection of various metallic components by means of solder. However, the above-mentioned use of copper and soldr gives rise to special problems resulting from the close proximity of the copper and solder to a salt bath furnace operating at a relatively high temperature. These problems are aggravated by the fact that the copper and solder are actually interconnected with the molten salt so far as heat conduction is concerned, by means of the metal of the electrodes.

In view of the foregoing it can be seen that it is highly desirable to minimize the transfer of heat from the region of the furnace to the region of the power source, and especially to avoid the conduction of excessive heat via the electrodes from the bath to the bus bar.

The primary object of the invention is the provision of an electric salt bath furnace electrode capable of ready assembly and disassembly with a power source bus bar in such a manner as to insure good electrical surface contact therebetween.

Another object of the invention is the provision of an electrode which includes a portion exposed to the cooling tendency of the atmosphere surrounding the furnace, which portion is constructed so as to expose a maximum quantum of surface area to the atmosphere in order to maximize the transfer of heat from the electrode to the atmosphere.

Still further the invention has as an object the provision, in an electrode of the kind just described, of means for utilizing a liquid coolant in order to supplement the cooling action of the atmosphere.

Other objects and advantages of the invention will be clear from the following description taken in connection with the accompanying drawing in which:

Figure l is a side elevational view, partly in vertical section, showing a furnace, power source and other parts associated therewith, together with an electrode according to the invention mounted in the furnace and connected to the power source;

Figure 2 is a perspective view (on an enlarged scale as compared with Fig. 1) of an electrode according to the invention together with a portion of an associated bus bar;

Figure 3 is a vertical sectional view taken along the line 3-3 of Fig. 2 but on an enlarged scale as compared with Fig. 2;

Figure 4 is a plan view on the scale of Fig. 3 showing an electrode according to the invention assembled with a bus bar; and

Figure 5 is a fragmentary sectional view taken generally along the line 5 -5 of Fig. 4 and illustrating a modification of the invention featuring means for liquid cooling of the electrode.

Preliminarily it is pointed out that, although the drawings illustrate the invention as embodied in a slant type electrode of the kind discussed above and claimed in my copending application previously identified, the invention is nevertheless capable of embodiment in various other types of electrodes. It is also mentioned that the invention can be used with a wide variety of types of furnace and power sources and is therefore not limited to use with the particular kind of furnace and power source illustrated in the drawings.

Referring to the drawings in more detail, the furnace F includes a pot P, cover C and one or more pairs of electrodes, each electrode E comprising a hot leg HL, cold leg CL and a portion IL intermediate the hot and cold logs. The transformer or power source T has horizontally extending stub bars S and S fastened respectively to vertical bus bars B and B which are in turn interconnected with the cold legs CL in a manner more fully'explained herebelow. It will be noted that the upper stub S and bus bar B interconnect with the cold leg CL which appears in Fig. 1 while the lower stub S and bus bar B pass behind stub S and bus bar B and interconnect with the cold leg of an electrode hidden from view in Fig. 1..

The furnace F comprises a number of supporting members 6, a base 7 and side supports 8 enclosing a thick layer of insulation 9 (capped with a course of fire brick 10) surrounding the pot P which may be built up from a plurality of tiles 11. The pot is filled with salt 12 up to level 13. Cover C is provided with rollers 14 adapted to travel along tracks 15 in response to manual pushing or pulling by means of the handle 16 which may pivot (upwardly from the position shown) about the pin 17 into a convenient horizontal position. The cover C may be shifted between a forward position (illustrated in Fig. 1) in which it generally overlies the pot and a rearward position (not shown) in which the pot is exposed to accommodate the insertion or removal of parts being treated in the furnace.

Inorder to minimize the contact of atmosphere with the intermediate portion IL in the region of the salt bath level, the furnace wall may be chamfered as at 18, and various tiles such as 19 and 20 may be provided closely surrounding the electrode, all as more fully disclosed and claimed in my copending application identified above. A thermocouple 21 may be provided in order to measure the temperature of the bath.

The electrodes may be clamped in place by means of bolts 22 which pass through washers 23, insulators 24, 24 and the angle iron 25 secured to the side supports 8, the bolts cooperating with nuts 26 in order to provide for firmly holding the electrodes in place during operation while at the same time making possible relatively quick and easy disassembly for replacement or repair of the electrodes.

Attention is now directed to the features of the construction dealing more specifically with the invention herein. As seen in Figs. 2, 3 and 4, the cold leg CL of each electrode comprises a plurality of laminations 27, 28 and 29 which are mounted in spaced parallel relation and secured to the intermediate portion IL, for instance by welds 36. (The intermediate portion IL is in turn welded to the hot leg HL by welds 31 and 32.) With this arrangement the cold leg is interconnected with the hot leg and adapted to extend out of the furnace for connection to a bus bar B which includes a plurality of spaced elements 33 and 34.

In the drawings the cold leg is illustrated as having three laminations and the bus bar as having two elements but it is understood that the number of laminations and elements can be varied. The total number of laminations is preferably equal to the number of bus bar elements plus one so that each bus bar element is clamped between two larninations. When the laminations are interleaved with the bus bar elements to form an assembly,

a lamination will occupy the outermost position on each side of the assembly for reasons discussed below.

Disengageable means for securing the assembly together are provided in the form of a plurality of bolts 35 adapted to pass through aligned apertures in the laminations and bus bar elements and to cooperate with nuts 36 which screw onto the threaded portions 37 of the bolts. The bolts and nuts comprise clamping means firmly holding the assembly together but capable of being readily and easily disassembled.

As best seen in Fig. 4, the central lamination 28 is conveniently substantially thicker than the outermost laminations 27 and 29, the embodiment shown in the drawings having a lamination 28 about twice as thick as either of laminations 27 or 29. Such an arrangement facilitates the drilling of coolant holes as discussed below in connection with Fig. 5. In addition, the thickened central lamination is desirable because this lamination is on contact with two bus bar elements instead of'only one as is the case with the outer laminations, and thus carries twice as much current as the outer ones.

An important feature of the invention is the arrangement of the laminations so as to provide air space 38 between laminations 27 and 28 and air space 39 between laminations 28 and 29. These air spaces 38 and 39 in effect virtually double the surface area of the cold leg CL exposed to the cooling efiect of the atmosphere 4 outside of the furnace. By this means it is possible to relatively rapidly dissipate into the atmosphere the heat conducted up the hot leg HL and intermediate leg IL before this heat reaches the copper bus bar elements 33 and 34 and miscellaneous solder connections referred to previously. In addition, the increased circulation of air and resulting cooling action has an important effect on the life of the electrode as a Whole and particularly on the life of the intermediate portion IL because of the fact that the intermediate portion is thereby maintained at a lower temperature during operation. In this connection it should be kept in mind that electrode corrosion becomes a more and more significant problem as the operating temperature increases.

As a further aid in maintaining a relatively cool cold leg CL, the modification shown in Figure 5 provides for passage means 49 and 41 in the interior of the central lamination, the mouths of such passage means conveniently being threaded as at 42 to cooperate with piping or other conduits (not shown) in communication with a source of liquid coolant, such as water.

Various prior devices utilized cold legs similar in construction to the hot leg and intermediate leg shown in the drawings, that is, a single solid bar type of construction. Ordinarily such devices provided for connection with power source bus bars by merely drilling holes through the solid cold leg and bus bar portions, assembling a bus bar on each side of the cold leg with the holes aligned, and then passing bolts through the holes and tightening nuts on the bolts, usually with ordinary circular Washers inserted between the bolt heads and bus bar on one side and between the nuts and bus bar on the other side. However, particularly in view of the fact that the copper is relatively soft and malleable, a construction involving ordinary bolts, nuts and washers does not result in good surface contact between the electrode and bus bar. On the contrary, since the copper tends to bulge slightly out of contact with the electrode as a result of the squeezing action at the point or line of bearing contact between the washer and copper, this type of construction results in scattered small points of tight contact surrounded by areas where there is no or only light contact. From an electrical standpoint, this is highly undesirable.

In contrast with the foregoing, the present invention provides for the establishment and maintenance of tight surface contact between the laminations and bus bar elements. The outermost laminations 27 and 29 each in clude a rigid portion having a surface adapted for contact with a cooperating surface on the bus bar, the two cooperating surfaces being substantially coextensive and extending across substantially the entire width of the bus bar. Stated in another way, each of the outermost laminations includes a continuous rigid bearing surface extending across and adapted to contact substantially the entire width of the bus bar. The resulting assembly together with the clamping means described, insures good electrical conductivity between the electrode and bus bar. The laminations 27 and 29 are thick enough and are constructed of material which is rigid enough to withstand any tendency to bul e locally out of tight surface con tact with the bus bar. In efiect, it might be said that the outer laminations provide for a thick and rigid Washer underlying all of the bolt heads on one side and another such washer underlying all of the nuts on the other side.

The construction described above also provides for the effective use of both sides of each bus bar element in carrying current to the cold leg of the electrode.

For instance, in Figure 3, current carried by bus bar element 33 will flow into the cold leg of the electrode into the central lamination 28 from one of its faces and into outside lamination 29 from its opposite face. Likewise, bus bar element 34 will deliver half of its current approximately through one face to lamination 28 and the other half to lamination 27.

genomes The center lamination 28 carries double the current of side laminations 27 and 29 and is, as mentioned above, generally about twice as thick for this reason.

It is also pointed out that the provision of air spaces, such as 38 and 39, results in another substantial advantage. Since the temperature of the cold leg assembly during operation is maintained lower than would be the case if a single solid bar type of cold leg were used,

it is possible to fabricate the laminations of the cold leg from ordinary readily available steels. it is not necessary to resort to the use of high alloy steels (which are relatively expensive and sometimes scarce) as is necessary when the cold leg material is subjected to higher temperatures during operation.

Iclaim:

1. An electrode for use with an electric salt bath furnace comprising, a hot leg adapted to protrude into the salt, and a cold leg interconnected with the hot leg and adapted to extend out of the furnace for connection to a bus bar including a pair of spaced elements carrying electric current, said cold leg comprising three laminations mounted in spaced parallel relation and adapted to interleave with said elements of the bus bar, and clamping means for establishing and maintaining tight surface contact between said laminations and bus bar elements.

2. An electrode according to claim 1 in which the central lamination has interior passage means adapted to accommodate the flow of a liquid coolant.

3. An electrode for use with an electric salt bath furnace comprising, a hot leg adapted to protrude into the salt, and a cold leg interconnected with the hot leg and adapted to extend out of the furnace for connection to a bus bar including a plurality of spaced elements carrying electric current, said cold leg comprising a number of laminations mounted in spaced parallel relation, the number of said laminations being equal to the number of said bus bar elements plus one, the laminations and bus bar elements being adapted to interleave with each other to form an assembly With a lamination outermost on each side of the assembly, and disengageable means for securing the assembly together, whereby to provide for the establishment and maintenance of tight surface contact between the laminations and bus bar elements.

4. An electrode for use with an electric salt bath furnace comprising, a hot leg adapted to protrude into the salt, and a cold leg interconnected with the hot leg and adapted to extend out of the furnace for connection to bus bar means carrying electric current, said cold leg comprising a plurality of laminations mounted in spaced parallel relation and adapted for assembly with the bus bar means with a lamination in outermost position, on each side of the assembly, said outermost laminations each including a rigid portion having a surface adapted for contact with a cooperating surface on the bus bar means when assembled therewith, said cooperating surfaces extending across substantially the entire Width of the bus bar means, and means for clamping the assembly together whereby to maintain tight contact between said cooperating surfaces.

5. An electrode for use with an electric salt bath furnace comprising, a hot leg adapted to protrude into the salt, and a cold leg interconnected with the hot leg and adapted to extend out of the furnace for connection to a bus bar including a plurality of spaced elements carrying electric current, said cold leg comprising a plurality of laminations mounted in spaced parallel relation and adapted for assembly with the bus bar elements with a lamination in outermost position on each side of the assembly, said outermost laminations each including a continuous rigid bearing surface extending across and adapted to contact substantially the entire width of the adjacent bus bar element when assembled therewith, and means for clamping the assembly together, whereby to insure tight surface contact between the laminations and bus bar elements over substantially the entire area of said bearing surface.

6. An electrode for use with an electric salt bath furnace comprising, a hot leg adapted to protrude into the salt, and a cold leg interconnected with the hot leg and adapted to extend out of the furnace for connection to a bus bar including a plurality of spaced elements carrying electric current, said cold leg comprising a number of laminations mounted in spaced parallel relation, the number of said laminations being equal to the number of said bus bar elements plus one, the laminations and bus bar elements being adapted to interleave with each other to form an assembly with a lamination outermost on each side of the assembly, and means for clamping the assembly together to maintain tight surface contact between the laminations and bus bar elements, whereby to provide two paths for current flow between each bus bar element and the laminations clamped thereagainst, one of said paths being through the surface of one side of the bus bar element and the other of said paths being through the surface of the other side of the element.

References Cited in the file of this patent UNITED STATES PATENTS 2,347,400 Csepely Apr. 25, 1944 2,421,224 Solakian et al. May 27, 1947 2,487,770 Lepsoe Nov. 8, 1949 2,508,004 Adam May 16, 1950 2,701,269 Holden Feb. 1, 1955 FOREIGN PATENTS 440,564 Great Britain Dec. 30, 1935 

